Lighting Wiring Consideration.

Further to the funny current rating, in my Grandfather's ICS (International Correspondence Schools) library of building and construction techniques, from the same sort of era, that sadly went west when he died, was a section introducing  the then new-ish  electricity, including a table of cable ratings that based cable ratings on 1000 amperes per square inch, as a pure scaling of current with cross-section, although there was a foot note that more recent developments suggested that this rule tended to overheat larger conductors, and underestimate the capacity of thinner conductors they being better able to cool. I guess at that time some of the subject was was still in the air, and temperature  testing had just not been done on enough types of cable.

It also had wonderful illustrations of wiped joints in plumbing and cutting bricks and many other things as well - the electrics was just one chapter.

It may be that Zooms's table of current ratings dates or at least was copied from, an era when the detail of how to deduce the current ratings of smaller cables was still a matter of doubt.


I guess the way to see is to compare a number of other cross-sections in the same book, and see if the ratings look like they are in proportion to area

I'm sure there were cotton wrapped dry paper insulated singles available as well, which is what I was imagining, are they on another page by chance ? Clearly however they would not have been suited to immersion before  testing at a pressure of 1000V, so indoors only !!

M.

Further to the funny current rating, in my Grandfather's ICS (International Correspondence Schools) library of building and construction techniques, from the same sort of era, that sadly went west when he died, was a section introducing  the then new-ish  electricity, including a table of cable ratings that based cable ratings on 1000 amperes per square inch, as a pure scaling of current with cross-section, although there was a foot note that more recent developments suggested that this rule tended to overheat larger conductors, and underestimate the capacity of thinner conductors they being better able to cool. I guess at that time some of the subject was was still in the air, and temperature  testing had just not been done on enough types of cable.

It also had wonderful illustrations of wiped joints in plumbing and cutting bricks and many other things as well - the electrics was just one chapter.

It may be that Zooms's table of current ratings dates or at least was copied from, an era when the detail of how to deduce the current ratings of smaller cables was still a matter of doubt.


I guess the way to see is to compare a number of other cross-sections in the same book, and see if the ratings look like they are in proportion to area

I'm sure there were cotton wrapped dry paper insulated singles available as well, which is what I was imagining, are they on another page by chance ? Clearly however they would not have been suited to immersion before  testing at a pressure of 1000V, so indoors only !!

M.